<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>天气案例_监视属性_简写</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>

    <div id="root">
        <h2>今天天气很{{info}}</h2>
        <button @click="changeWeather">切换天气</button>
    </div>
</body>

<script type="text/javascript">
    Vue.config.productionTip = false;

    const vm = new Vue({
        el: '#root',
        data() {
            return {
                isHot: true
            }
        },
        computed: {
            info() {
                return this.isHot ? '炎热' : '凉爽';
            }
        },
        methods: {
            changeWeather() {
                this.isHot = !this.isHot;
            }
        },
        watch: {
            // isHot: {
            //     // immediate: true,
            //     // deep: true,
            //     handler(newValue, oldValue) {
            //         console.log('isHot被修改了', newValue, oldValue);
            //     }
            // }

            // 简写
            isHot(newValue, oldValue) {
                console.log('isHot被修改了', newValue, oldValue);
            }
        }
    })

    // vm.$watch('isHot', {
    //     immediate: true, // 初始化时让handler调用一下
    //     handler(newValue, oldValue) {
    //         console.log('isHot被修改了', newValue, oldValue);
    //     }
    // })

    // 简写
    vm.$watch('isHot', function (newValue, oldValue) {
        console.log('isHot被修改了', newValue, oldValue);
    })
</script>

</html>